The most disagreeable problem to wearer comfort and visual acuity of contact lenses is the presence of contaminants on the surface of the lens. Those contaminants, for the most part, are proteins, lipoproteins, and other contaminants (hereinafter referred to as "contaminants") produced by the eye, tear duct, and eyelid for lubrication and protection of delicate optic tissues. Contaminants will collect on the surfaces of non-permeable lenses to form small protrusions which rub against the sensitive ocular tissues to promote inflammation and discomfort.
There are a number of known methods for removing contaminants from a contact lens surface including the use of a mild detergent to wash the lens surface and the use of a proteolytic enzyme which digests the protein molecules. However, these methods are only partially effective and may, in some cases, damage the lens.
Other methods of removing protein from contact lens are shown in a number of patent references. For example, U.S. Pat. No. 4,921,544 (Cowle et al.) discloses a method wherein the contact lens is placed in an electrophoretic solution within a container, an electric field is applied to the solution through two electrodes in the solution, and the charged protein molecules attached to the lens migrate to the oppositely charged electrode. However, in this method, migration eventually reaches an equilibrium at which point it becomes very difficult to remove additional proteins from the solution. U.S. Pat. No. 4,872,965 (Pankow) offers a method wherein electrodes are immersed in solution baths external to the lens and current is provided to the lens by a transmission means which rests on the lens surface. From this point, the contaminants are removed from either the lens surface or from the electrochemical transmission means by an additional wiping step. This method was particularly adaptable to clean lenses made from hydrophilic materials which absorb large proportions of water within the lattice they create.
U.S. Pat. No. 5,292,372 (Swaisgood et al.) is directed to a method of removing contaminants from permeable contact lenses (an adsorbent is used with the contact lens so the adsorbent is disposed between the lens and an electric current source). The immersed lens, adsorbent and current source are positioned in a container which holds an aqueous saline solution, and an electric current is applied from the source through the adsorbent and through the lens so that contaminants removed from the lens migrate to the adsorbent.